Means and techniques useful in prestressing concrete structures

ABSTRACT

In wrapping wire around a concrete tank to prestress the same, a carriage is caused to travel around the tank by a motor-driven sprocket wheel thereon engaging a chain which extends tightly around and on the tank. Simultaneously the wire is fed from a supply spool onto a wire-gripping drum and is then laid on the outer tank wall with a wire tension established by monitoring deviations in stress with respect to a nominal value of stress, and using such deviations to produce changes in the differences in peripheral linear speed between, on the one hand, the sprocket wheel speed (carriage speed) and on the other hand the linear speed of the wire-gripping drum. Such stress is maintained substantially constant at the same nominal value whereby the wire is uniformly and accurately stressed when and as it is being wrapped around the tank wall. A platform carrying wire tensioning apparatus may be raised or lowered on the carriage during carriage movement, either in the forward direction or in reverse direction or when the carriage is at standstill. Means are incorporated to assure a constant spacing between wire convolutions. Also control means are incorporated to maintain constant tension regardless of carriage speed either in a forward or reverse direction or at carriage standstill. The wire may be laid in a continuous helix or in steps accurately controlled as to height. Also means are incorporated to achieve or maintain an automatic wire tension regardless of carriage movement in either direction of carriage movement or at standstill. Further, the wire may be tensioned from a slack or zero tension condition to any desired tension and maintained automatically at such tension without requiring carriage movement. Also, the desired tension may be preadjusted to any desired value while the carriage is in motion either in the forward or reverse direction. A hydraulicelectrical system is used for these purposes involving a hydraulic motor which drives the carriage connected in a unique manner with respect to a hydraulic motor/pump having its shaft connected to wire-gripping means.

United States Patent [15] 3,666,190 451 *May 30, 1972 Dykmans MEANS AND TECHNIQUES USEFUL IN PRESTRESSING CONCRETE STRUCTURES [72] Inventor: Maximiiiaan ,I. Dykmans, 4434 Mayopan Drive, La Mesa, Calif. 92041 [21] Appl.No.: $5,335

Related US. Application Data [63] Continuation-impart of Ser. No. 718,138, Apr. 2, 1968, Pat. No. 3,572,596, and a continuation-in-part of Ser. No. 49,277,.lune 24, 1970.

[52] [1.8. CI... ..242/7.21 [51] Int. Cl. ..B2li 17/00 [58} Field oiSearch ..242/7.21, 7.22, 7.23, 75.53

[56] Reierences Cited UNITED STATES PATENTS 3,572,596 3/1971 Dykmans ..242/7.21 2,321,465 6/1943 Crom... 242/723 X 2,520,402 8/1950 Hirsh ....242/7.22 2,573,793 11/1951 Kennisonm ..242/7.22 2,589,366 3/1952 Gauthier ..242/7.22 3,281,085 10/1966 Crom ....242/7.21 3,338,527 8/1967 Chidzey... ....242/7.22 3,379,385 4/1968 Osweiler ..242/7.22

Primary ExaminerStanley N. Gilreath Assistant ExaminerMilton Gerstein Attorney-Lyon & Lyon ABSTRACT in wrapping wire around a concrete tank to prestress the same, a carriage is caused to travel around the tank by a motor-driven sprocket wheel thereon engaging a chain which extends tightly around and on the tank. Simultaneously the wire is fed from a supply spool onto a wire-gripping drum and is then laid on the outer tank wall with a wire tension established by monitoring deviations in stress with respect to a nominal value of stress, and using such deviations to produce changes in the differences in peripheral linear speed between, on the one hand, the sprocket wheel speed (carriage speed) and on the other hand the linear speed of the wire-gripping drum. Such stress is maintained substantially constant at the same nominal value whereby the wire is uniformly and accurately stressed when and as it is being wrapped around the tank wall. A platform carrying wire tensioning apparatus may be raised or lowered on the carriage during carriage movement, either in the forward direction or in reverse direction or when the carriage is at standstill. Means are incorporated to assure a constant spacing between wire convolutions. Also control means are incorporated to maintain constant tension regardless of carriage speed either in a forward or reverse direction or at carriage standstill. The wire may be laid in a continuous helix or in steps accurately controlled as to height. Also means are incorporated to achieve or maintain an automatic wire tension regardless of carriage movement in either direction of carriage movement or at standstill. Further, the wire may be tensioned from a slack or zero tension condition to any desired tension and maintained automatically at such tension without requiring carriage movement. Also, the desired tension may be preadjusted to any desired value while the carriage is in motion either in the forward or reverse direction. A hydraulic-electrical system is used for these purposes involving a hydraulic motor which drives the carriage connected in a unique manner with respect to a hydraulic motor/pump having its shaft connected to wire-gripping means.

6 Claims, 8 Drawing figures MEANS AND TECHNIQUES USEFUL IN PRESTRESSING CONCRETE STRUCTURES The present application is a continuation-impart of my pending U.S. application, Ser. No. 718,138 filed Apr. 2, 1968 now U.S. Pat. No. 3,572,596, issued Mar. 30, 197i and also my pending application Ser. No. 49,277, filed June 24, l970.

The present invention relates to improved means and techniques which are particularly useful in the prestressing of concrete structures such as, for example, reservoirs, nuclear reactors, pressure vessels in general, and pressure pipes. It will be appreciated that the invention in its broader aspects is useful for other purposes such as, for example, laying cable under controlled tension.

A specific object of the present invention is to provide improved means and techniques whereby a uniform and accurate stressing of wire is obtained in the process of wrapping the same around cylindrical structures.

Another specific object of the present invention is to provide a system of this character in which the wire tension is automatically adjusted so as to make such wire tension substantially constant in intensity.

Another specific object of the present invention is to provide a system of this character in which stresses are monitored to derive information as to the condition in the wire and using such information in a manner as to change relative speeds between carriage travel and the rate at which the wire is wrapped to thereby obtain constant tension in the wire during the wrapping process.

Another specific object of the present invention is to provide a system of this character in which a hydraulic system is controlled in accordance with changes in stress so as to minimize variations in such stress.

Another specific object of the present invention is to provide an improved system which provides automatic control of wire tension under all conditions.

The features of the present invention, which are believed to be novel, are set forth in particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 illustrates relationship of apparatus with respect to a concrete wall of a tank around which a carriage effectively pulls itself while laying wire on the tank in a stressed condition.

FIG. 2 is generally a view in side elevation and partly in diagrammatic form illustrating the wheeled carriage with the vertically adjustable platform carried thereon.

FIG. 3 is an electrical diagram illustrating connections to various components which are mounted on the vertically movable platform shown in FIGS. 1 and 2.

FIG. 4 illustrates means in which one of the switches shown in FIG. 3 is actuated.

FIG. 5 illustrates the manner in which the individual wire strands S are spaced using the apparatus described herein.

FIG. 6 illustrates a hydraulic control system mounted on the vertically movable platform in FIGS. I and 2.

FIG. 7 illustrates a modification.

FIG. 8 illustrates element of a lock off" shown also in FIG. 2.

ln FIGS. 1 and 2, a sprocket chain C encircles the outer wall W of the concrete structure T. The chain C may be considered stationary, particularly since the major length of the same is in nonsliding contact with wall W. The chain C is used to propel the wheeled carriage 7 having wall-engaging wheels 8 and ground-engaging wheels 9. This carriage 7 mounts a platform 5 which is vertically adjustable on carriage 7 and which carries the mechanism for propulsion of the carriage 7 around the wall and for simultaneously laying or wrapping wire or strand S around the wall under tension. As illustrated in FIG. I, such chain C passes in turn in this order over: guide sprockets 2 and 3, spring-loaded tensioning sprocket 4 urged by spring 4A, drive sprocket 22 on shaft 10 and sprocket wheel 20. The

arrangement 85 drive sprocket 22 is on shaft 10 which also mounts a larger sprocket wheel 33. A drive chain 32 extends over wheel 33 and sprocket wheel 31 on the output shaft of hydraulic drive motor 30. Thus, it will be seen that operation of motor 30 causes the carriage 7 with platform 5 thereon to move around the circular tank wall W for purpose of wrapping cable, wire, or strand S around such wall.

The wire, strand, cable, or the like, S, which is wrapped around the wall W with tension uniformly and accurately being applied to such cable during such wrapping extends from a supply reel R, which may be mounted on carriage 7, to and around a wire-gripping drum 2] (which is coaxially mounted with the previously mentioned sprocket wheel 20 but which may rotate independently of the same on different shafts 20A, 21A as illustrated in FIG. 2) and then to the structure wall W for prestressing of the same. At the point where the wire 8 first engages the drum 2!, the wire is spring-urged against such drum by device 6 for purposes of assuring a nonslip condition between the wire and its gripping drum 2].

The wire-gripping drum has a sprocket wheel 218 secured thereto as illustrated in FIG. 2 with a chain 41 extending over such wheel 21B and a sprocket wheel 42 on shaft 40.

The wire 8 is tensioned and thus stretched as a result of the lineal speed of the carriage 7 being somewhat greater than the rate at which the wire S is laid on the wall, i.e., assuming that the effective diameters of sprocket wheel 20 and wire drum 21 are the same, as they may be in practice, the sprocket wheel 20 rotates somewhat faster than the wire-gripping drum 21 to cause the wire to be stretched and thus tensioned. For that purpose, rotation of wire drum 2] is impeded in controlled manner.

It is of importance that such tensioning be uniformly and accurately established during the wire wrapping operation; and for that purpose, the system described herein is of particular usefulness.

In FIG. 2, the shaft 10 driven by motor 30 also drives the input shaft of hydraulic motor 360. A hydraulic motor/pump 361 has its outputs shaft 11 coupled to a sprocket wheel 15. A chain I6 passes over sprocket l5 and a sprocket 16A on shaft 40 so that the wire drum sprocket 21 B and connected wire drum 21 rotate together at a speed determined by the rotational speed of shaft 40 which is controlled as presently described.

The hydraulic motor 360 and motor/pump 361 have their outlets interconnected by conduit 360 B, 361 B in which a Tee connection is provided which leads to the sump 360 C via check valve 360 D. A hydraulic pump 370 driven by control motor 92 has its outlet connected via check valve 371 to the inlet lines 360 A, 361 A of motor 360 and motor/pump 361 respectively, such pump 370 having its inlet connected to sump 360 C.

The control motor 92 is controlled by the output of a servo system 97 having two inputs which are compared in system 97 and functioning to control motor 92 in accordance with such comparison. One of such inputs is a current or voltage derived from a torque transducer 100 associated with shaft 40 in such a manner as to produce such current or voltage that changes in intensity with the torque being applied to shaft 40. The other input is a manually adjustable input derived from the tap 102 on potentiometer resistor 103 having its outside terminals connected to opposite terminals of voltage source 104. As a result of any change in torque in shaft 40, from a nominal value, there is a change in the output of servo system 97 to cause the motor 92 to rotate at a different speed which in turn causes the shaft 40 to rotate at a different speed until the torque sensed by transducer 100 is restored to such nominal value. In other words, a self-balancing system is provided such that the tension of wire S, related to the torque in shaft 40 is maintained substantially constant during the operation of the system.

The mechanism previously described for propulsion and controlled wire laying is all mounted on the platform 5. The platform 5 is slidably mounted in the carriage 7 and is vertically adjustable therein so that successive convolutions of wire laid on the tank wall may be of a different elevation. Preferably the wire wrapping is started at the bottom of the tank with the platform being raised each time the carriage makes one revolution around the tank.

The platform 5 is held in the position to which it is adjusted by a cable 200 having one of its ends secured to the platform 5 at region 5A and its other end wound around a winch drum after passage over a supporting pulley 203 rotatably mounted on the upper portion of carriage 7 at 7A. This drum 202 is drivable by the output shaft 205 of a hydraulic winch motor 206 which is supplied with hydraulic fluid from pump 207 via hydraulic line 208, solenoid valve 209 and hydraulic lines 210. The pump 207 is driven by the motor 30 via shaft 10, sprocket wheel 212 on shaft 10, chain 214, and the input sprocket wheel 215 of pump 207. In one position of selector valve 209 as explained later, fluid may be returned to the sump 220, in which case the winch drum remains stationary, i.e., the platform 5 remains in a stationary adjusted position when and as the carriage 7 is being propelled by power being applied to motor 30. The winch drum 202 has coaxially mounted therewith for movement therewith a socalled cam wheel 222 which is preferably of the same diameter as the drum 202 for operation of a control switch LS 2 for purposes described later.

Accurate control of the spacing between adjacent convolutions of wire, i.e., the pitch is achieved using the switches LS 1 and LS 2 in FIG. 2 which are electrically connected with other elements in a pitch control circuit 240 as now described with reference to the lower, left-hand portion of FIG. 3 which shows this pitch control in addition to other electrical circuitry described later.

The switch LS I is in the form of a microswitch on carriage 7 and has its actuating element movable into engagement with a stationary post 242 on the ground whereby such switch LS l is actuated at least once per revolution of the carriage 7 around the tank T.

The switch LS 2 as shown in FIGS. 2 and 4 has its actuating element cooperating with the cam wheel 222 which has cams spaced thereon one-eighth of an inch apart so that for each one-eighth of an inch peripheral movement of the cam 222, the switch L8 2 is operated through an On-Off-On cycle. When, as preferred, the diameter of the cam wheel 222 is equal to the diameter of the winch drum 202 (FIG. 2) this 5- inch movement corresponds to one-half of that movement or one-sixteenth of an inch movement of the platform 5 because of the manner in which it is supported by cable 200.

These switches LS l and LS 2 are normally closed switches, and each as seen in FIG. 3 are associated with a so-called Eagle type counter device 246 which incorporates a clutch winding 247 and a so-called advance winding or coil 248. The energization of winding 247 results in operation of the normally closed switch 247 A as indicated by dotted line 247 B, and energization of coil 248 results in operation of normally closed switches 248 A and 248 B as indicated by the dotted lines 248 C and 248 D.

The control circuit is energized by 120 V AC applied between leads L l and L 2.

Switch LS I and winding 247 are in series between lines L I and L 2. Switches LS 2, 248 B and coil 248 are in series between lines L l and L 2. Switches 247 A and 248 A are in a series circuit with relay coil 250 between lines L 1 and L 2; and when coil 250 is energized, it operates its associated relay switches 250 A and 250 B as indicated respectively by dotted lines 250 C and 250 D. It is noted that the series circuit comprising switches 247 A, 248 A is bridged or shunted by a manually operable normally open push button type switch 254, termed a job switch for obtaining small movement of the platform 5 when the carriage 7 is in movement. Switch 250 A when closed energizes the pilot light 256. The other relay switch 250 B is connected in a control circuit for the solenoid valve 209 for control of the platform raising and winch motor 206 (FIG. 2); and for that purpose, the solenoid valve 209 has correspondingly two windings 209 A, 209 8. Either one or neither one of these solenoid valve windings 209 A, 209 B may be selected for energization depending upon the position of a three-position, manually operable selector switch 260 having an Oil position, a Raise" position, and a Lower" position. The switch 260 is illustrated in its Raise" position wherein the lead 26! is connected to one terminal of coil 209 A having its other terminal connected to the minus lead 264 of DC power supply 265. In the Lower" position, lead 261 is connected to one temiinal of winding 209 B having its other terminal connected to lead 264. In the "Off" position of switch 260 neither one of the windings 209 A, 209 B is energized. This lead 261 is connectable to the other positive lead 267 of source 265 via a two-position manually operable switch 270 having either an "Automatic" or a Manual position. In the Manual position, leads 261 and 267 are interconnected directly; in the Automatic position these two leads 261, 267 are connectable via the previously mentioned relay switch 250 B which is connected in series with the switch 270 in its Au tomatic" position.

The operation of this pitch control circuit is now described under the condition that switch 270 is adjusted to its Automatic" position and switch 260 is in its Raise" position. It will be understood that the counter 246 is of the type which is manually adjustable to respond to and produce a control operation in accordance with each of a predetermined number of pulses applied thereto. Thus the counter, known commercially as an Eagle Cycle-Flex counter, may be ad justed such that the number of counts may be from one to 40 in number, depending upon the desired wire pitch. For example, the desired wire pitch is eleven-sixteenths inch and the counter is manually adjusted to respond in succession to only each of the first 1 1 counts or digits developed by the cam disc 222 of the cable winch drum 202 (FIGS. 2 and 4). The counter 246 is automatically reset to its assumed preadjusted count of l 1 upon operation of switch LS 1 by stationary post 242 (FIG. 2). This assures initiation of the pitch control of wire S always on a point on the vertical line 280 (FIG. 5). Once the counter 246 is reset at 280 to 11, preset count of l l the wire S is then no longer laid horizontally as indicated by the wire distance Sl S2, but the succeeding wire section S2, S3 is inclined due to raising of the platform 5; and when the vertical line 282 Is reached (corresponding to point S3), the wire is again laid horizontally without any upward or downward movement being imported to the plntiorm 5 when and as the carriage 7 is being propelled around the tank T so that consequently the points S3, S4, S5, and 86 are in the same horizontal plane. At point S6 the post 242 again causes the switch LS l to be actuated to again allow a lifting of platform 5. This wire pattern illustrated in FIG. 5 b not dependent upon the speed of carriage travel, i.e., the same results regardless of speed of carr'lage travel or changes in speed oi carriage travel or whether or not the carriage may have been in a standstill condition somewhere between lines 280 and 282. This is so because the position of platform 5 is made independent of the position of carriage 7 as a result of using the some prime mover 30 and special pump 207 driven by such motor or engine 30.

Returning to the operation of the pitch control circuit in FIG. 3 opening of switch LS 1 results in energization of clutch 247 and resetting of the counter switch 247 to its assumed preset ll count. This I I count is counted down one digit at a time each time switch LS 2 is operated (FIG. 4). During this countdown, switch 247 A is closed to condition a circuit for relay coil 250. Thus, with switch 247 A closed, the relay coil 250 is energized to close switch 250 B to thereby connect solenoid valve raise coil 209 A between DC lines 267, 264 in which case hydraulic power is supplied to the winch motor 206 (FIG. 2) which then rotates winch drum 202, and this rotation continues to cause the switch LS 2 to be operated. The first time switch LS 2 is operated, the platform 5 is raised one count, i.e., one-sixteenth inch, and the count of the counter switch 246 is reduced from an initial count of 11 to the count of 10. After the eleventh count, i.e., the counter reads zero and the switches 248 A and 248 B remain open, thereby deenergizing relay coil 250 and preventing energizetion of the solenoid valve. This condition prevails until the carriage 7 is moved around the tank to again operate switch LS 1 and thereby reset the counter switch 247 to the preset 11 count. Manual override or jogging of the platform may be accomplished to change wire spacing if desired by operating pushbutton switch 254 which causes relay coil 250 to be energized. Such jogging may result in either upward or downward movement of the platform 5 depending upon whether switch 250 is initially adjusted to its "Raise or its Lower" position. Selector switch 270 in Manual" position enables a direct manual control through the Raise" or lower" contacts of selector switch 260, even if part or the entire automatic-pitchcontrol circuit is or becomes inoperable. This means that the amount of pitch can be controlled manually without the use of the automatic pitch control circuit. By simply working the selector switch 260 from its Off" position to its Raise" position, it is possible to develop manually the required amount of pitch simulating the purpose of the automatic pitch control circuit.

It will be appreciated that instead of having only one such post 242, a plurality of such posts may be spaced around the tank T all for the purpose of resetting the counter switch 246 by actuation of switch LS 1 as previously described. Also, instead of beginning the wire wrapping at the lower portion of the tank and proceeding upwardly, the wrapping may, if desired, be accomplished in a downward direction, in which case the selector switch 260 is in its Lower" position.

It will be further appreciated that the distance between lines 280 and 282 may be decreased or increased as desired and indeed this distance may at one extreme correspond substantially to the circular distance around the tank, in which case the pitch is considered as being of constant inclination without horizontal stretches of the wire. This latter mode of constant inclination may be achieved simply by adjusting switch 270 to its Manual" position. The faster carriage 7 goes around the tank, the faster proportionally is the platform raised or lowered as the case may be. This is assured by use ofa variable control pump 207 whose output is related proportionally to the speed of the motor or engine driven shaft 10. This pump 207 continues to pump hydraulic fluid when the three position switch 260 is in its "011'" position, in which case the fluid is not delivered under pressure to the winch motor 206 but is allowed to return to the sump 220.

Further details of the hydraulic system are illustrated in FIG. 6 where the hydraulic system includes three pumps 300, 301, and 207. Pump 301 is required to have the largest capacity and it serves to supply fluid under pressure to the motor 30 for driving the carriage 7 around the tank. In such case, the fluid flow is from the reservoir 220 through the valve 306 and filter 307 to the inlet of pump 301 and delivered under pressure to the selector valve 309 and forward and reverse valve 310 from whence the fluid is delivered to hydraulic motor 30.

The pump 301 is a so-called stem control pump in that it incorporates a large lever which may be moved manually to produce a continuous change in speed of motor 30, starting from zero speed to maximum speed. The valve 309 is a selector valve which transfers fluid flow either to motor 30 as described above or to the platform winch motor 206 via the solenoid valve 209 in which latter case the platform may be raised or lowered, depending upon the energization of solenoid valve coil 209 A or 209 8 (FIG. 3) without requiring movement of the tower for that purpose. The fluid in this latter instance flows through valve 309, check valve 315, and through valve 209 to winch motor 206. In this regard, it is noted that the pump 207 is not operating because it requires for its operation movement of the carriage 7, i.e., rotation of shaft 10 which chain drives the sprocket drive 215. Check valve 316 prevents flow from valve 309 to the outlet of pump 207. Jogging of the platform 5 may be accomplished using push button switch 254 or may be moved continuously by adjusting the switch 270 to its "Manual" position, (FIG. 3).

This large pump 30! is driven by a gasoline engine 320 which serves also to drive the pump 300 for supplying fluid under pressure to the servo motor 92 for the automatic control of wire tensioning and detensioning in the process of winding the wire S under the desired constant tension.

Pump 300 is a pressure compensated pump delivering fluid under substantially constant pressure. The flow of fluid is from reservoir or sump 220 through valve 306 and filter 307, through pump 300, servo valve 332 to the servo motor 92 whose shaft 96 drives the pump 370.

The motors 360 and 361 may be of the so-called high torque, low RPM type and are preferably of identical construction.

The inlet line 360A to motor 360 which is connected to pump outlet line 361A may have a pressure of, for example, 2000 p.s.i. (pounds per square inch) and its outlet line 3608 which is connected to pump inlet line 3618 may have a pressure of, for example 50 psi.

Motor 361, capable of acting as a pump and motor 360 maintain a balance of forces. Thus, should, for example, the torque in shaft 40 exceed a nominal value, a corresponding output is developed on output lead 78 so as to reduce the outlet pressure of pump 370 and cause a reduction in the differential speed between drive sprocket 20 and wire drum 21 to restore the torque in shaft 40 to its nominal value.

The other hydraulic motor 30 is supplied with substantially constant pressure from pump 301 and rotates the chain sprocket 20 which causes the carriage to be driven forward. During the travel of the carriage 7 the motor 361 is driven by the drum with the motor 361 acting as a pump to supply ener gy to the motor 360.

Hydraulic motors with a straight torque-RPM characteristic (linear relation between torque and speed) may be used in some instances without a load cell, i.e., stress sensor in which case the oil pressure may be sensed and corrective measures taken to maintain the same at a preadjusted magnitude. Also other ones of many different conditions representative of stress and/or differential speed may be sensed by a corresponding transducer and the output of such transducer then used to restore such condition to a nominal value. Such condition sensed may, for example, be power input to an electrical or hydraulic system, current, voltage, fluid pressure, amount of fluid flow, speed, effectiveness of a braking action or the like.

The servo valve 332 receives an output from amplifier 340 to which a command signal is supplied from potentiometer 103 on the control panel 341. Another input to amplifier 340 is the output of preamplifier 343 which receives an input from the torque load cell 100 and provides a signal which is applied to the tension indicator 344 on panel 341. This tension indica tor 344 may be of the visual type such as to produce a digital indication, but is preferably a recorder for purposes of achieving an ink permanent record of tension.

A permanent type paper recorder is illustrated also at 344 in FIG. 3. It may be of the type supplied by Hewlett-Packard with conventional recording paper advancing mechanism which is operated in accordance with a signal applied thereto via leads 350 from the output of amplifier 352 having an input signal developed in accordance with the actuation of switch 368, such switch 368 being a proximity type switch which as shown in FIG. 2 is mounted adjacent to a magnet 368A extending from shaft 40 and is actuated thereby upon rotation of shaft 40. The pulses developed upon actuation of switch 368 are used to move the paper of recorder 344 a distance proportional to the number of such pulses processed in proximity amplifier 352 so that the distance traveled by the paper upon which a recording is made is a measure of the amount of wire S that has been wound on the tank. The signal recorded is applied to the recording signal input terminal 362, 3637 Terminal 362 is connected to the output of amplifier 343 as is also digital meter 344 A, the other terminal 363 and the other terminal of meter 344 A are connected to an adjustable reference point on resistance 365 which is connected across the load cell power supply 370. Thus, a permanent record is available of the tension present in each portion of the wire as it was wound.

It is noted for the foregoing purposes that the output of amplifier 340 is applied to the servo valve 332 in the normal Run position of the two position, manually adjustable switch 380 in which case the amplifier output is applied via connected switch contacts E, F, and U to the terminals 384, 385 of valve 332, in which case either positive or negative voltages as the case may be are continuously applied to valve 332 in the process of maintaining constant wire tension. It is sometimes desirable to adjust this tension manually using a jog-type control and to maintain the same, independently of peration of load cell 100, in which case switch 380 is actuated to its other Stop position to thereby disconnect the servo valve 332 from the amplifier and to connect lead 390 to terminal 384 via contacts G and H and to connect terminal 385 via switch contacts K and L to the common ground lead 392 and at the same time to apply the command voltage on the tap of command potentiometer 103 via resistances 394, 395 and switch contacts C, D, and E to an output terminal of amplifier 340 by a feedback path which includes a connection between the junction point of resistances 394, 395 to one terminal of amplifier 340. With lead 390 so connected to terminal 384, either a positive or a negative voltage may be applied to such terminal by correspondingly closing the Forward" jog push button switch 396 or the Reverse" jog pushbutton switch 397 as desired via corresponding speed adjustment resistances 388, 389. Thus, in the Stop position of switch 380, the tension in the wire may be manually increased or decreased and the tension may be observed on meter 344A and recorded on meter 344.

In normal operation when the carriage 7 is moving and a constant tension is being maintained by the servo system, variations either below or above a nominal speed serves to increase or decrease the tension to restore the tension to its nominal adjusted value. When the carrige 7 is in a standstill condition, i.e., stationary, the motor/pump 361 serves as a motor to maintain constant tension in the wire.

When maintaining constant tension with carriage movement, there is, of course, a difference in speed between, on the one hand the sprocket and the wire gripping drum 21. Hence, there is a requirement that the motor/pump 361 act as a pump.

In certain circumstances it is desired to obtain a rapid engagement or disengagement of the wire from gripping drum 21, and this may be done by operating switch 380 to its "Stop" position and operating job switches 396 or 397. Important uses, for example, of this jogging control are for purposes of developing maximum speed for threading a new wire strand through the system; tensioning or detensioning the wire that has previously been applied to the tank wall and which for some reason or another may be required to be removed and replaced.

ln automatic operation, it is noted to increase the wire tension with the carriage 7 moving the tension control potentiometer 103 is adjusted. The servo system then functions so that the newly adjusted input voltage is summed with a voltage derived from the load cell 100, and this algebraic sum by action of the system is automatically reduced to zero. Should there be any slippage of the chain on the tank and hence a change in relative speeds such that the tension tends to change, the servo system quickly functions automatically to minimize or nullify any change in wire tension.

An important feature of the present system involves the fact that the wire tension may be adjusted without the need for moving the carriage. With the carriage stationary, adjustment of resistance 103 to a different setting either lower or higher, causes the servo motor 92 to drive the pump 370 to cause the wire-gripper drum 21 to move in a corresponding direction. This may be accomplished not only by adjustment of resistance 103 but also by operating the jog switches 396 or 397. In this latter instance, the tension change may be accomplished more rapidly.

Another important feature of the system is that wire tension is maintained constant not only during forward wire laying movement of the carriage 7 but also in those instances where the carriage 7 is being moved in the reverse direction as, for example, when it is desired to return to a socalled wire clamping ofi' point on the tank wall or to correct wire spacing. In this latter regard, the structure of the wire gripper is of important, and for that reason, the wire gripper described in my US. Pat. No. 3,5l0,04l, issued May S, 1970 is preferred because lack of wire tension on one side does not destroy the gripping action as is the case, for example, when a conventional capstan or drum is used. Using a wire gripper of the character described in that patent, wire slack may be tolerated.

Another important feature of the present system involves the fact that the platform 5 may be raised or lowered at carriage standstill with full power using the carriage pump 301 and selector valve 309 in its condition wherein it supplies fluid under pressure to motor 206. It is noted again that at standstill, pump 207 does not function because it requires carriage movement for its operation.

it is noted in particular that the vertical movement of platform 5 during horizontal carriage movement may be controlled by setting of the counter 246 (FIG. 3) and/or by adjustment of flow of pump 207 using handwheel control 207A which serves to control or adjust the volume of fluid being supplied to motor 206. The higher the volume of fluid supplied to motor 206 the higher is the speed of vertical platform movement; and hence, the greater the slope of the wire being laid as exemplified by the slope of the line 82-83 in FIG. 5. ln deed, when the switch 270 (FIG. 3) is in its ManuaP position the slope of the wire is such that a continuous helix is formed because in such case the counter circuit 246 has no control function, assuming, of course, that the selector switch is in Raise" or Lou/er" position.

The pump 300 is as indicated previously as pressure regulated or compensated pump for purposes of delivering sufficient constant pressure under all conditions. The pump 301 is a socalled manually operable stem control pump which through manual adjustment is capable of delivering an oil flow in continuous infinite steps from zero to maximum flow capacity with the flow rate being substantially directly proportioned to the amount of manual stern movement. The pump 207 is a variable volume type pump, the output volume of which may be controlled by a handwheel control 207 A and when such handwheel is adjusted, the flow of fluid is directly proportioned to the speed of input sprocket 216 (FIG. 2), i.e., directly proportional to speed of carriage 7. In some cases the handwheel control 207A is adjusted for zero fluid flow in which instance carriage movement produces no vertical movement of platform 5. In other cases, the handwheel control 207 A may be adjusted for maximum flow in those in stances where it is desired to accomplish a steep raising or lowering of the platform 5.

In operation, at carriage standstill and preparatory to feeding wire to drum 2] to take up initial slack. It is assumed, of course, that one end of the wire is anchored to the tank. To take up slack, the tap on resistance 103 is adjusted to provide an increased voltage to the servo control 97. This causes the control motor 92 to operate the pump 370 which is a variable volume type pump in the sense that the delivered volume increases with increase of rotation of shaft 96. By so increasing the volume of delivery to line 360A, the motor/pump 361 serves as a motor to rotate shaft 40 and wire drum 21 to reel in the wire slack. At this stage due to friction in the carriage system, the motor 360 having its shaft connected directly to shaft 10 may be considered to be stationary. The wire slack then continues to be reeled in to the condition where the wire ultimately becomes stressed, and such stress is monitored by load cell which supplies a proportionate voltage signal to the servo control 97, which is compared to a signal derived from tap 102. When these two compared signals are equal, representing a particular wire tension a comparable pressure is developed and maintained in line 361 A. Because as a practical matter there is some oil leakage in the motor/pump 361 (also in motor 360) back to the reservoir via return lines 361 F and 360 F the pump 370 is driven at sufficiently high speed to supply such oil leakage and, this means that in the balanced condition of the servo system, the motor 92 rotates at a minimum reduced speed. Instead of that servo system illustrated in FIG. 2 controlling pump 370, such pump in accordance with broader aspects of the present invention may be controlled by other means such as, for example, as shown in FIG. 7 where in this modification the pump 470 (comparable to pump 370 in FIG. 2) is an adjustable pressure-compensated pump whose delivery pressure may be manually adjusted to maintain a particular selected pressure in line 360 A related to the desired wire tension. Such adjustable means is represented at 470 B which may be a screw-threaded sensitive adjustment.

At this stage the carriage is still considered stationary and o eration is now described when the carriage moves as a result of fluid pressure being supplied to motor 30 which causes shaft 10 to rotate. It is observed that shaft 10 is driven not only by pressure applied to motor 30 but also by pressure being applied to motor 360. When the carriage moves, the wire drum 21 rotates and acts as a prime mover to operate motor/pump 361 as a pump in which case such pump 361 pumps oil into line 361 A to the hydraulic motor 360 in energy feedback relationship. Assuming that during such carriage movement the preset tension in the wire decreases, this decrease is sensed by torque transducer 100 which causes the motor 92 to rotate faster to cause the pump 370 to deliver a greater oil flow to hydraulic line 360 A to provide sufficient oil under pressure in such line to restore the wire tension to its preset nominal value. When this assumed decrease in wire tension exists in the modification shown in FIG. 7, the pump 470 automatically senses a drop in pressure in line 360 A and automatically functions to restore such pressure to maintain the desired wire tension. When the wire tension tends to increase, the same type of action results with a pressure balancing operation causing the torque in shaft 11 being again restored to a nominal value. During system shutdown, using the modification of FIG. 7, the motor 470 A continues to operate to maintain the desired oil pressure, and hence desired torque in shaft 11, i.e., desired wire tension. This condition is maintained during those times when the motor 30 is not operated, in which case the motor/pump 361 functions as a motor. Subsequently, when it is desired to completely shut down the system (including motor 470 A in FIG. 7) the system may initially be locked-ofi' mechanically using the brake drum system illustrated in FIGS. 2 and 8. Such system involves a circular plate P secured to sprocket 20, a circular plate 21 P secured to sprocket wheel 2] B and a pair of hinged semicircular friction bands 401, 402 which may be drawn together by suitable screw threaded adjustable means 404 to clamp the two plates 40], 402 together and thereby prevent relative rotation.

Also, it will be observed that the initial slack in the wire may be taken up by operation of the jog switch 396 in initial manual feeding of the wire to the machine.

As to the size of the motors 360, 361 and 30, the motors 360, 361 as mentioned previously may be of the same size. They, however, are much higher in horsepower capacity than motor 30. The motors 360, 361 and 30 may be of the piston or vane types.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

Iclajm:

1. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circurnferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; the last mentioned means including a first hydraulic motor operable also as a pump; a second hydraulic motor; means coupling said first motor to said movable element such that the same may be driven thereby; means coupling said second motor to said carriage moving means for moving the carriage around said circular structure; additional drive means hydraulically independent of said second motor and coupled to said carriage moving means for moving the carriage around said circular structure; and a pump for supplying fluid under pressure to said first and second motors.

2. A system as set forth in claim 1 including means releasably interconnecting said element with said carriage moving means to prevent relative movements therebetween.

3. A system as set forth in claim 1 in which said pump is a pressure compensated pump which delivers a constant pres sure to said first and second motors.

4. A system as set forth in claim 3 including manually adjustable means for adjusting the pressure of said ressure compensated pump to thereby adjust the tension of said wire.

5. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; said carriage moving means including a rotatable shaft; first means coupled to said shaft for rotating the same; first motor means operable also as an energy generating means and coupled to said element for driving thereby; second motor means coupled to said shaft for rotating the same; a source of energy for second motor means; means interconnecting said first motor means with said second motor means to transfer energy therebetween.

6. A system as set forth in claim 5 including means for maintaining the level of said energy at a constant value. 

1. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; the last mentioned means including a first hydraulic motor operable also as a pump; a second hydraulic motor; means coupling said first motor to said movable element such that the same may be driven thereby; means coupling said second motor to said carriage moving means for moving the carriage around said circular structure; additional drive means hydraulically independent of said second motor and coupled to said carriage moving means for moving the carriage around said circular structure; and a pump for supplying fluid under pressure to said first and second motors.
 2. A system as set forth in claim 1 including means releasably interconnecting said element with said carriage moving means to prevent relative movements therebetween.
 3. A system as set forth in claim 1 in which said pump is a pressure compensated pump which delivers a constant pressure to said first and second motors.
 4. A system as set forth in claim 3 including manually adjustable means for adjusting the pressure of said pressure compensated pump to thereby adjust the tension of said wire.
 5. In a system of the character described wherein a carriage moves around a stationary circular structure to lay and tension wire on the same, a carriage for movement around said stationary circular structure; means for supporting said carriage adjacent to the outer wall of said circular structure for circumferential movement around said circular structure; a wire supply; means for gripping wire supplied thereto from said wire supply; said gripping means including at least one movable element; means for moving said carriage around said circular structure; means controlling movement of said movable element such that a tension is developed in said wire; said carriage moving means including a rotatable shaft; first means coupled to said shaft for rotating the same; first motor means operable also as an energy generating means and coupled to said element for driving thereby; second motor means coupled to said shaft for rotating the same; a source of energy for second motor Means; means interconnecting said first motor means with said second motor means to transfer energy therebetween.
 6. A system as set forth in claim 5 including means for maintaining the level of said energy at a constant value. 